By John Michaelides
By John Michaelides
Three major groups of compounds play a pivotal role in the function and
existence of all living things. These are carbohydrates, fats or oils,
and proteins. Of all these, the most important and complex are the
Three major groups of compounds play a pivotal role in the function and existence of all living things. These are carbohydrates, fats or oils, and proteins. Of all these, the most important and complex are the proteins.
Proteins are made of building blocks, including amino acids, which are arranged in a sequence to form the of protein types that exist in nature. Plants using nitrogen and other simple compounds and the sunlight as an energy source synthesize these amino acids. Animals are unable to synthesize amino acids and therefore rely on plants for such a supply to build up their own proteins.
Proteins are mainly composed of carbon (50-55 per cent), oxygen (20-23 per cent) and nitrogen (12-19 per cent). Of these, nitrogen is the most important.
Normal analysis of food products and ingredients relies on the amount of the nitrogen for the determination of the protein content. As a basic rule, the nitrogen content of a food can be multiplied by 6.25 to determine the protein content of that food. However, this can only produce an approximate number because the 6.25 factor is based on an average nitrogen content of 16 per cent and the nitrogen content of proteins varies from 12 to 19 per cent.
In some cases, other factors can be used if the nitrogen content of the specific protein is well established. For example, in the case of wheat, the accurate factor for whole kernel is 5.83, for bran it’s 6.31, and for the endosperm (flour) it’s 5.7. For convenience, however, the factors of 6.25 and 5.7 are normally used.
Because we determine the protein content of foods indirectly based on the amount of nitrogen content, this leads to occasional food adulteration issues. The food industry’s recent problems with melamine adulteration emphasizes this inadequacy. Melamine contains high nitrogen, and by adding it to foods or ingredients we can elevate their protein content.
In 2008 in China, melamine in dairy products caused the deaths of six people and made thousands ill. Thus, manufacturers of certain foods have to adhere to mandatory levels of protein content, resulting in adulteration attempts. To combat the adulteration of foods with melamine, China has recently lowered the required minimum levels of protein in such foods.
Proteins from different sources have different nutritional values, determined by the combination of the amino acid composition.
Proteins play an important role as functional ingredients. They provide structure and texture, viscosity, foaming and water binding, colour and flavour, many other roles. Proteins such as egg albumin traditionally have been important in the production of cakes and other baked goods.
Because of the high cost of such ingredients, much research has been done to find cheaper alternatives. Indeed, protein isolates and concentrates from soy and whey, as well as other plant sources, have been introduced as substitutes for the role that egg albumin plays in baked goods. These ingredients have enjoyed limited success, as substantial reformulation efforts are required to remove or reduce the egg albumin.
Proteins are complex and unique, and their functionality is often attributed to their complexity. Their structure and configuration in many cases plays a role in their function in biological and food systems. For example, enzymes are proteins and it is their structural configuration that determines their ability to attach themselves to substrates on which they act as catalysts.
Enzymes are widely used in the food industry and recently have been found to be very important tools for the baking industry. They are used to improve wheat flour performance, reduce the effect of staling, and replace or reduce other unfriendly chemicals used in baking.
In the baking industry, many sources of protein, are used as functional ingredients. However, the most functional as they are applied to baking are the natural proteins that form the gluten. Two major proteins are found in wheat flour that, when combined with water and energy (mixing), will develop the gluten matrix and form the dough. They are gliadin and glutenin, and when developed into gluten they are responsible for gas retention in the dough and the characteristics of bread and related products as we know them.
For this reason, these proteins were recognized as early as the 16th century as playing a role in the quality of the wheat flour. In the past hundred years, many researchers have contributed to the elucidation of the role of these proteins in wheat flour functionality. In turn, this research provided the basis of the process of industrial production of bread and other baked goods.
The functionality of wheat proteins varies from variety to variety, and crop to crop. Although quite often wheat and flour are sold on the basis of their protein content, a high amount of protein does not necessarily mean that their quality is high as well. Flour manufacturers often resort to other tests to determine the quality of the protein before it is sold to the industry.
Proteins play a very important role as biological agents in living things but also as components of foods. Incorporating proteins into food products fulfils two major purposes: as nutrition enhancement and as functional ingredients, allowing us to process and produce valuable food products.
Dr. John Michaelides is Guelph Food Technology Institute’s director of research and technology. For more information, or fee-for-service help with product or process development needs, please contact GFTC at 519-821-1246 or firstname.lastname@example.org.